There are 3 principal objective of this research project. One is to gather and integrate information on the effects of gonadal hormones on several behaviors in rodents, focusing on behaviors which affect body weight and composition. A second goal of this project is to study some of the molecular mechanisms by which sex hormones act upon neural and nonneural target tissues to affect behaviors. The third goal is to study the effects of diabetes mellitus, overweight, and underweight on behavioral responsiveness to sex hormones. Previous work from this laboratory indicates that gonadal hormones have important effects of behavioral regulation of body weight in a wide range of mammalian species, ranging from rodents to primates. Specific projects focus on sites and pathways of hormone action in brain and peripheral tissues. Molecular endocrinologists have provided a great deal of information on the subcellular mechanisms of steroid action. The second portion of this project uses some of their techniques to correlate binding of hormones in target tissues with effects on sexual behaviors and regulatory behaviors. diabetes mellitus, obesity, and underweight are all associated with impaired reproductive performance in human beings and experimental animals of both sexes. The third portion of this project examines the effects of these disturbances on reproductive behaviors and target tissue hormone binding in rats.